Conventionally, optical coherence tomography apparatuses (hereinafter, referred to as OCT apparatuses) have been applied to ophthalmic practice such as tomographic imaging of a cornea and/or a retina of an eye in the biomedical fields. The OCT allows for non-invasive and non-contact diagnosis by irradiating a living tissue with light. Examples of a known diagnostic system other than the OCT include: CT (Computed Tomography) with resolution of 200 micrometers or less; MRI (Magnetic Resonance Imaging) with resolution of 800 micrometers or less; and PET (Positron Emission Tomography) with resolution of 1000 micrometers or less. Compared with these systems, the OCT can achieve by far superior resolution from several to several dozens micrometers, and can display a high-resolution precise image. It has been known that the OCT systems can be classified roughly into TD (Time Domain)-OCT and FD (Frequency Domain)-OCT. The latter FD-OCT can be further classified into SD (Spectrum Domain)-OCT and SS (Swept Source)-OCT.
For example, in the SS-OCT, a laser source is used to continuously sweep wavelengths (wave numbers); and spectral information as obtained using a detector is subject to FFT (Fast Fourier Transform) processing to specify an optical path length. The SS-OCT has a higher resolution than X-ray equipment and CT devices, which are widely used in dental practice, and is characterized in that a real-time measurement can be performed without being exposed to radiation.
Meanwhile, the above-described TD-OCT has been tested for dental practice. The SS-OCT, however, can acquire data faster with higher sensitivity than the TD-OCT. Thus, the SS-OCT has a motion artifact (a ghost due to body movement)-resistant feature.
In order to obtain a tomogram, the OCT apparatus requires two-dimensional mechanical scanning in a widthwise direction (a left-right direction with respect to an object) and in a lengthwise direction (a front-rear direction with respect to the object), which are perpendicular to a laser beam direction (a vertical or depthwise direction with regard to the object) facing the object. Unfortunately, the imaging and diagnosis conventionally take a long time.
A technology (see JP2010-142428A) regarding an ophthalmic OCT apparatus has been known that prior to acquisition of a detailed image used for diagnosis, an overview of an object is obtained.
An imaging apparatus disclosed in JP2010-142428A includes: a tomographic image acquisition section whose function is implemented by an OCT apparatus; and a front image acquisition section whose function is implemented by a fundus camera or an SLO (Scanning Laser Ophthalmoscope) to acquire a front image. The front image acquisition section is to obtain an overview of an object.
In addition, in the dental fields, a handpiece for a dental optical diagnostic apparatus includes OCT means. Then, means for positioning an optical diagnosis site in a tooth is implemented by a camera imaging system, which includes an imaging camera for acquiring a surface image (see Japanese Utility Model Registration Application No. 3118718). Accordingly, the camera image can be used for prior positioning.